The present invntion relates to an electrostatic display module made capable of providing variable-sized pixels.
An electrostatic display element as shown perspectively in FIG. 6(a) and cross-sectionally (along line A--A of FIG. 6(a)) in FIG. 6(b) can be used as a pixel element in a pattern display board by constituting the board with many such electrostatic display elements arranged, for example, in the form of a matrix. In principle, the electrostatic display element consists of an assembly of a pair of fixed electrodes 1 and 2 kept oppositely to each other and a movable electrode 3 positioned therebetween. The fixed electrodes 1 and 2 are coated on their confronting surfaces with differently colored elecrically insulating layers 11 and 21 and have their respective middle frank portions made curved inwardly to form hemi-cylindrical inward prostrusions 12 and 22. The movable electrode 3, which is usually made of a metal-plated mirror-faced flexible thin film, is hold by a film holder 4 and then, together with a terminal plate 5, secured between the fixed electrodes 1 and 2 at their flat portions under the hemi-cylindrical inward protrusions 12 and 22 with electrically insulating spacers 6 and 7 interposed. In such a mechanical constitution of the element, the fixed electrodes 1 and 2 are kept voltage-supplied, while the movable electrode 3 is electrically switched selectively to either of the fixed electrtodes 1 and 2. If the movable electrode 3 is switched to the fixed electrode 2, the movable electrode 3, whose potential is made equal to that of the fixed electrode 2, is attracted by and to the fixed electrode 1 (and repelled by and from the fixed electrode 2) to bend toward the fixed electrode 1, masking the insulating layer 11 on the fixed electrode 1 and exposing the layer 21 on the fixed electrode 2. At such a posture of the movable electrode 3, the layer 21 is not only exposed but also reflected by the mirrored surface of the movable electrode 3. Thus, the electrostatic display element, seen from above, appears to have the color of the insulating layer 21. Needless to repeat a similar description, if the movable electrode 3 is switched to the fixed electrode 1, the electrostatic display element comes to be represented by the color of the insulating layer 11. Since the appearance of the electrostatic display element is thus changed according to the potential selection of the movable electrode 3, the element can be used as a pixel of a pattern display board.
Further, though the pixel made of such an element as shown in FIGS. 6(a) and 6(b) is rectangular because of the rectangular-shaped opening on top of the pair of fixed electrodes, a square pixel, if desired, can be constituted by combining two such electrostatic display elements into one unit with the individual fixed electrode pairs arranged in parallel to each other. Examples of such are seen in some embodiments of the present invention.
Whether the pixel is square or not, its size is determined by the size of the electrostatic display elements used. On the other hand, a larger display pattern to be seen more remotely can generally be constituted of relatively large-sized pixels, and a smaller display pattern be seen less remotely is necessarily constituted of small-sized pixels in general. In other words, the size of pixels depends on an apparent resolving power required of a display board. This means that the pixels, that is, the electrostatic display elements must be designed inconveniently in accordance with the size or the resolving power of an objective display board to be constituted.